Associations between social isolation, pro-social behaviour and emotional development in preschool aged children:a population based survey of kindergarten staff

Peer reviewedPublisher PD

Pathogenic Neisseria Hitchhike on the Uropod of Human Neutrophils

Polymorphonuclear neutrophils (PMNs) are important components of the human innate immune system and are rapidly recruited at the site of bacterial infection. Despite the effective phagocytic activity of PMNs, Neisseria gonorrhoeae infections are characterized by high survival within PMNs. We reveal a novel type IV pilus-mediated adherence of pathogenic Neisseria to the uropod (the rear) of polarized PMNs. The direct pilus-uropod interaction was visualized by scanning electron microscopy and total internal reflection fluorescence (TIRF) microscopy. We showed that N. meningitidis adhesion to the PMN uropod depended on both pilus-associated proteins PilC1 and PilC2, while N. gonorrhoeae adhesion did not. Bacterial adhesion elicited accumulation of the complement regulator CD46, but not I-domain-containing integrins, beneath the adherent bacterial microcolony. Electrographs and live-cell imaging of PMNs suggested that bacterial adherence to the uropod is followed by internalization into PMNs via the uropod. We also present data showing that pathogenic Neisseria can hitchhike on PMNs to hide from their phagocytic activity as well as to facilitate the spread of the pathogen through the epithelial cell layer

Investigation of the Genes Involved in Antigenic Switching at the vlsE Locus in Borrelia burgdorferi: An Essential Role for the RuvAB Branch Migrase

Persistent infection by pathogenic organisms requires effective strategies for the defense of these organisms against the host immune response. A common strategy employed by many pathogens to escape immune recognition and clearance is to continually vary surface epitopes through recombinational shuffling of genetic information. Borrelia burgdorferi, a causative agent of Lyme borreliosis, encodes a surface-bound lipoprotein, VlsE. This protein is encoded by the vlsE locus carried at the right end of the linear plasmid lp28-1. Adjacent to the expression locus are 15 silent cassettes carrying information that is moved into the vlsE locus through segmental gene conversion events. The protein players and molecular mechanism of recombinational switching at vlsE have not been characterized. In this study, we analyzed the effect of the independent disruption of 17 genes that encode factors involved in DNA recombination, repair or replication on recombinational switching at the vlsE locus during murine infection. In Neisseria gonorrhoeae, 10 such genes have been implicated in recombinational switching at the pilE locus. Eight of these genes, including recA, are either absent from B. burgdorferi, or do not show an obvious requirement for switching at vlsE. The only genes that are required in both organisms are ruvA and ruvB, which encode subunits of a Holliday junction branch migrase. Disruption of these genes results in a dramatic decrease in vlsE recombination with a phenotype similar to that observed for lp28-1 or vls-minus spirochetes: productive infection at week 1 with clearance by day 21. In SCID mice, the persistence defect observed with ruvA and ruvB mutants was fully rescued as previously observed for vlsE-deficient B. burgdorferi. We report the requirement of the RuvAB branch migrase in recombinational switching at vlsE, the first essential factor to be identified in this process. These findings are supported by the independent work of Lin et al. in the accompanying article, who also found a requirement for the RuvAB branch migrase. Our results also indicate that the mechanism of switching at vlsE in B. burgdorferi is distinct from switching at pilE in N. gonorrhoeae, which is the only other organism analyzed genetically in detail. Finally, our findings suggest a unique mechanism for switching at vlsE and a role for currently unidentified B. burgdorferi proteins in this process

Chloride currents in acutely isolated Xenopus retinal pigment epithelial cells

The retinal pigment epithelium (RPE) regulates the ionic composition of the fluid surrounding the photoreceptors by transport mechanisms that utilize Cl− channels. Cl− currents in RPE cells, however, remain incompletely characterized. The purpose of this study was to identify the Cl− currents in acutely isolated Xenopus RPE cells using whole-cell patch clamp. We describe three different Cl− currents. (1) An inwardly rectifying Cl− current, ICl,ir, activates slowly with hyperpolarization (τact=μ1 s at −80 mV, V1/2=−94 ± 3 mV), is blocked by Zn2+ (IC50=185 μm), is stimulated by acid (ICl,ir is 5 times larger at pH 6 than pH 8), and is blocked by DIDS in a voltage-dependent manner. ICl,ir closely resembles cloned ClC-2currents. (2) An outwardly rectifying Cl− current, ICl,Ca, is stimulated by elevated cytosolic free [Ca2+]. With 1 μm free [Ca2+]i in the patch pipette, ICl,Ca activates slowly with depolarization (τact=325 ms at 100 mV) and deactivates upon hyperpolarization. ICl,Ca is not blocked by 1 mm Zn2+ or 10 μm Gd3+ but is blocked by DIDS. High extracellular [Ca2+] (10 mm) also activates ICl,Ca. (3) A non-rectifying current is activated by elevation of cytoplasmic cAMP with forskolin and IBMX. In addition to these three Cl− currents, Xenopus RPE cells exhibit a non-selective background current (Ibkg) which has a linear I-V relationship and is voltage insensitive. This current is blocked by Zn2+ (IC50 of 5.3 μm) or 10 μm Gd3+. This description provides new insights into the physiology of Cl− channels involved in salt and fluid transport by the retinal pigment epithelium